In the past, a tractor operator generally used the center crease in the hood of the tractor as the sight for maintaining the tractor in its properly centered position relative to crop rows. It has been found however, that there is a significant variation in the positioning of a tractor by different operators, because some people are right eye dominated and others are left eye dominated. The dominant eye is that which is used for establishing a single line of sight. Most operators align the tractor hood crease or ornament with the guide furrow for centering the tractor, but the lines of sight of a left eye dominated operator and a right eye dominated operator will result in substantially different positions of the tractor relative to the furrow.
To resolve this problem, the present inventor developed the furrow follower vision correction system described in U.S. Pat. No. 4,401,166. That system includes a laterally adjustable tractor sighting device which can be adjusted by various operators to accommodate their particular positioning on the tractor seat and dominate eye. Thus, by simple lateral adjustment of the sighting device, all operators can easily maintain a uniform and centered position of the tractor relative to planted rows or crops or any other visible centerline.
Whereas the device of U.S. Pat. No. 4,401,166 is believed to be a significant advance in the art, a problem is encountered with the use of this device on hilly terrain. Even on hills, the sighting device is affected only slightly, if at all, by the tractor driving directly up or down a sloping surface. The problem occurs when the tractor drives transversely across the side of a hill whereupon the wheels on one side of the tractor are elevated above the wheels on the opposite side of the tractor. This canting of the tractor toward the downhill direction causes the operator's line of sight through the laterally adjusted sighting device to be offset from the centerline being followed by the tractor.
To resolve this problem, the present inventor developed the centerline sight with reverse pendulum described in U.S. Pat. No. 4,511,005. That device includes an upstanding pivotally mounted sight with a depending pivotally mounted pendulum interconnected such that the pendulum will pivot as the tractor tilts which will thereby move the sighting device.
While the device of U.S. Pat. No. 4,511,005 solved many problems specifically related to tractors which are constantly canted to one side or the other, another problem arises when the tractor is driven neither directly up or down a sloping surface nor around a hill at a constant canted angle. Rather, the ground surfaces typically will cause the tractor to assume a position traveling uphill or downhill while also being canted to one side or the other. In addition, soil conditions will cause the tractor to slide slightly as it moves along in this uphill or downhill canted position. This problem is believed to be resolved by the centerline sight of the present invention.
Accordingly, a primary object of the present invention is to provide an improved centerline sight for a tractor.
Another object is to provide a centerline sight for a tractor which is laterally adjustable to compensate for the various driving positions and dominant eyes of the various operators.
A further object of the present invention is to provide a laterally adjustably centerline sight which is equipped to maintain a proper line of sight when the tractor is laterally canted and longitudinally tilted.
Another object is to provide a centerline sight which is variable to adjust for different sizes and types of tractors as well as different types of soil.
Yet another object is to provide a laterally adjustable centerline sight which is simple and rugged in construction, inexpensive to manufacture, and efficient in operation.
These and other objects will be apparent to those skilled in the art.